This application seeks to study molecular mechanisms underlying the formation of orderly (tonotopic) connections in the auditory brainstem. The pathway to be studied is the projection of bushy cells of the anteroventral cochlear nucleus into the medial nucleus of the trapezoid body (MNTB). The project has two aims. First, the time course and growth patterns of innervation of MNTB will be studied using time-lapse imaging of fluorescence labeled axons. Second, candidate molecules that might be involved in axon guidance and target identification will be screened from core samples of MNTB. The spatial pattern of expression of these candidate molecules will be studied in organotypic slice cultures using in situ hybridization and immunocytochemistry.